1. Technical Field
The present invention relates to an engine valve seat having excellent wear resistance, particularly an engine valve seat in which an iron-based powder alloyed with chromium (Cr) and molybdenum (Mo) is used as a matrix, and a method of manufacturing the same.
2. Description of the Related Art
FIG. 1 is a sectional view showing a conventional engine valve seat. Generally, a valve seat 14 of an engine 10 is fitted in a cylinder head 12 to maintain the airtightness between an intake valve or an exhaust valve 16 and the cylinder head 12 when the valve 16 opens and closes. The valve seat 14, thus, serves to increase the thermal efficiency of a combustion chamber.
Because the valve seat 14 repeatedly comes into contact with the valve 16 and is exposed to continuous high temperatures, it typically requires higher wear resistance, impact resistance, heat resistance and the like than other parts.
Methods for manufacturing the valve seat 14 include an infiltration method, a hard particle addition method, an alloy composition control method and the like. In the past, gasoline containing lead (“leaded gasoline”) has been used as fuel. However, because the use of leaded gasoline causes environmental pollution, the use of unleaded gasoline is now required. Therefore, the valve seat 14 must have high performance, much like the high performance of engines, and must also generate high power and employ gasoline direction injection (GDI).
In engines using gas fuel such as liquefied petroleum gas (LPG), compressed natural gas (CNG) or the like, the valve seat 14 tends to be easily worn. In particular, use of such fuel generally does not provide the solid lubricity between the valve 16 and the valve seat 14 which typically results from the combustion products occurring when liquid fuel (gasoline, diesel oil) is used Thus, without such lubrication, metal contact (K) between the valve 16 and the valve seat 14 easily occurs, resulting in wear on the valve seat 14. Under such circumstances, the wear resistance of the valve seat 14 for gas fuel engines must be further improved.
In an attempt to improve the wear resistance of the valve seat 14, a method of dispersing Fe—Cr or Fe—Mo based hard particles or carbide-based hard particles in the matrix of the valve seat 14 has been used. However, this method is problematic in that, when the amount of hard particles dispersed in the matrix increases, the aggressiveness of the hard particles against a target (that is, a valve) increases, and thus the valve is more easily worn.
It is to be understood that the foregoing description is provided to merely aid the understanding of the present invention, and does not mean that the present invention falls under the purview of the related art which was already known to those skilled in the art.